aoc24: day05 filter invalid

sol/24/aoc.cpp

@@ -1,5 +1,6 @@
 #include <span>
 #include <expected>
+#include <string>
 
 #include "aoc.hpp"
 #include "ctre.hpp"
@@ -11,7 +12,7 @@ auto entry([[maybe_unused]]std::span<char const*> const& args) -> std::expected<
     u32 day = 1;
     if (args.size() > 1) {
         if (ctre::match<"^[0-9]+$">(args[1]))
-            day = std::stoul(args[1]);
+            day = u32(std::stoul(args[1]));
         else
             fmt::print(stderr, "arg: {} is not a number\n", args[1]);
     }